The major goal of the Clinical Core is to serve as a resource for the Neuropathology Core and proposed Center Projects and to facilitate other investigations at JHMI requiring human subjects with well-characterized PD. Accordingly, the specific aims of the Clinical Core are: 1. To identify, recruit, characterize clinically, and follow longitudinally until death patients with idiopathic Parkinson's disease and healthy controls who consent to eventual autopsy, thereby providing material for the Neuropathology Core and the neuropathologic studies in Projects #1-4. Clinical characterization will involve assessment of the motor, cognitive, and psychiatric features of PD. 2. In conjunction with the Administrative Core and Biostatistician, to develop and maintain a computerized database of all clinical data obtained on participating subjects, and to provide ongoing quality control and statistical support for studies in the Center grant using this information. These data will also be available to investigators within JHMI. 3. To provide the fundamental infrastructure for a clinical research program on PD that facilitates independently funded clinical and clinicopathological investigations of PD, and to coordinate the longitudinal subject assessments by the Clinical Core with subject participation in these additional studies. 4. To train physician-scientists in the clinical assessment and management of patients with PD and related disorders in the performance of clinical research on PD. The Clinical Core represents an opportunity to integrate clinical and basic research on PD in a multidisciplinary setting to expand ongoing clinical and basic research on PD in a multidisciplinary setting, to expand ongoing clinical research on PD at JHMI, and to initiate research contrasting PD with clinical and clinicopathological aspects of other neurodegenerative disorders. Human tissue is essential to research on the underlying disease mechanisms in PD.